Less than half of individuals living with HIV in the United States are receiving ongoing care, and only one- quarter have an undetectable viral load. The National HIV/AIDS Strategy prioritizes care and treatment of HIV- infected individuals, yet improvement in care retention rates is clearly needed. Research on HIV care has used attendance at primary care appointments to assess whether patients are in care. While medical visits are necessary, they are not sufficient and do not necessarily reflect a patient's level of engagement. Engagement in care is about the patient experience and interactions with providers and the care site. We propose to create a patient-centered Index of Engagement in HIV Care that will be framed within a model of Health Care Empowerment, which refers to participation in care in a way that is engaged, informed, collaborative, committed, and tolerant of uncertainty. We will create the index through a collaborative process of consensus- building with patients, providers, and research experts using iterative online Delphi surveys and in-person focus groups. We will then translate these narrative findings into scale items and develop them further through cognitive interviewing with patients. We will validate the index by administering i to a sample of patients undergoing the Patient Reported Outcomes within the CFAR Network of Integrated Clinical Systems (CNICS) and examining retrospective, cross-sectional, and prospective appointment and viral load data. The resulting Index of Engagement in HIV Care will have implications for both clinical care and research, identifying patients who are at risk fo poor clinical outcomes and providing a metric by which to develop and evaluate interventions aiming to improve engagement in care.